1. Field of the Invention
The present invention relates to a three-dimensional laminating molding device that forms three-dimensional objects using an inkjet system.
2. Related Art
A principle of a laminating molding is the same as that of a method for forming a three-dimensional contour map. That is, a three-dimensional object is sliced to produce sliced shapes, and then the sliced shapes are molded and laminated one on the other.
Examples of laminating molding methods include stereolithography using a photo-curing resin, powder lamination using metallic or resin powders, melt deposition in which resin is melted and deposited, and sheet lamination in which paper sheets, plastic sheets, or thin metal plates are laminated.
These laminating molding methods have spread rapidly along with a recent spread of a three-dimensional Computer Aided Design (CAD) and are also called rapid prototyping techniques. In these laminating molding methods, a three-dimensional object can be directly obtained from three-dimensional CAD data. The rapid prototyping technique is not only used in the field of trial manufacture, but also in the field of actual manufacture, since metallic molding has become possible. Further, by using a three-dimensional printer, a digitizer, or a scanner as an output device of a three-dimensional CAD, the rapid prototyping technique has become used also as a three-dimensional copying machine. In particular, a laminating molding device using an inkjet system is expected to be used in general-purpose three-dimensional printers or three-dimensional copying machines because the laminating molding device using an inkjet system has a simple configuration and is easy to handle compared with those using different system.
The laminating molding methods using an inkjet system are classified into a powder laminating method and a melt resin deposition method. The powder laminating method is developed by Massachusetts Institute of Technology. In the powder laminating method, binder is ejected into a powder layer of starch or plaster using an inkjet device, and then the ejected binder is cured. On the other hand, in the melt resin deposition method, resin is ejected to directly form a laminated shape without using any support layer.
The powder laminating method using powders requires a removal of unnecessary powders after molding and is not suited for an office environment because the powders scatter. Thus, the powder laminating method is less apt to a general-purpose three-dimensional printer or three-dimensional copying machine. On the other hand, the melt resin deposition method can be used in an office environment and is suited for the general-purpose three-dimensional printer or the three-dimensional copying machine.
The melt resin deposition method includes a method in which an arm of a robot attached with an ejection nozzle (the same as an inkjet head, in principle) is moved in three dimensions of XYZ and a method in which an inkjet head is placed in an X-Y plane and a Z direction. However, because these methods do not use a support for supporting a mold during molding process, floating island shapes (shapes that suddenly appear in layers when laminating sliced data) or long beam shapes, such as a crossbar of a letter H, could not be formed by these methods. Therefore, moldable shapes are restricted, and so these methods are not suited for forming complex shapes, such as practical industrial products and medical models.
As a counter measure for those, Japanese Patent No. 3179547 proposes a method that uses a support. Specifically, support resin and mold resin are both laminated, and a surface is planarized if necessary. By this method, even complex shapes can be molded. The support can be formed such that a mold is buried within the support. Alternatively, a columnar or tabular support can be formed at necessary places. However, the former method is preferable from a view of enabling correspondence to any complex shape and not requiring special data processing. (The latter method requires data processing for providing the support.)
Materials used in such an inkjet-type laminating molding are classified into materials which are liquid at room temperature and materials which are solid at room temperature. There has been proposed to use photo-curing resin or thermosetting resin, which is liquid at room temperature, for the inkjet-type laminating molding. However, if viscosity of the resin is high, then clogging occurs in nozzles, and on the contrary, if viscosity is low, then “dripping” occurs during photo-curing or thermosetting after lamination. Therefore, Japanese Patent No. 2697138 proposes to emit light in a flight path of the photo-curing resin droplets so as to irradiate the resin droplets in flight with the light. However, this method had a disadvantage that leakage light or reflected light irradiates an inkjet head, resulting in clogging of nozzles.
On the other hand, as a material which is solid at room temperature, resin which converts to liquid by heating, such as wax or hot melt resin, is often used. In Japanese Patent-Application Publication No. HEI-9-123290, the method in which a support is formed such that a mold is buried within the support is used, and materials with different melting points are used for the mold and the support so that the support can be removed by using a difference in melting points after mold process. However, those materials have some disadvantages. That is, these materials are brittle as a mold material, and the molds are easily broken. Further, these materials warp from shrinkage so that dimensional stability of the molds is impaired.
In order to overcome the brittleness of material, Japanese Patent-Applications Publication No. 2001-214098 proposes a mold material to which ductility is imparted.
Also, in order to maintain the dimensional stability of molds, Japanese Patent-Application Publication No. 2001-58357 proposes a method in which laminating molding is performed while performing a smoothing process using a revolving or high-temperature roller, a rotary cutter, or the like, every time a single layer or several layers of mold are formed. However, performing the smoothing process during the laminating molding process lowers a laminating molding speed.